Julie A. Culbert

Classification of Sparkling Wine Style and Quality by MIR Spectroscopy

In this study, the suitability of attenuated total reflection (ATR) mid-infrared (MIR) spectroscopy, combined with principal component analysis (PCA) and partial least squares (PLS) regression, was evaluated as a rapid analytical technique for the classification of sparkling wine style and quality. Australian sparkling wines (n = 139) comprising a range of styles (i.e., white, rosé, red, Prosecco and Moscato) were analyzed by ATR-MIR spectroscopy combined with multivariate data analysis. The MIR spectra of 50 sparkling white wines, produced according to four different production methods (i.e., Carbonation, Charmat, Transfer and Methodé Traditionelle) were also evaluated against: (i) quality ratings determined by an expert panel; and (ii) sensory attributes rated by a trained sensory panel. Wine pH, titratable acidity (TA), residual sugar (RS), alcohol and total phenolic content were also determined. The sparkling wine styles were separated on the PCA score plot based on their MIR spectral data; while the sparkling white wines showed separation based on production method, which strongly influenced the style and sensory properties of wine (i.e., the intensity of fruit versus yeast-derived characters). PLS calibrations of 0.73, 0.77, 0.82 and 0.86 were obtained for sweetness, tropical fruit, confectionary and toasty characters (on the palate), respectively.

The first total synthesis of natural grenadamide

A concise, high yielding route to the naturally occurring enantiomer of grenadamide utilizing a 3,6-disubstituted 1,2-dioxine starting material is presented. The route allows for ease in synthesizing grenadamide derivatives varying at cyclopropyl carbons 2 and 3, with access to both enantiomers. Evidence for phosphorus-assisted deprotonation of 1,2-dioxines is also discussed.

Influence of Production Method on the Chemical Composition, Foaming Properties, and Quality of Australian Carbonated and Sparkling White Wines

The chemical composition (protein, polysaccharide, amino acid, and fatty acid/ethyl ester content), foaming properties, and quality of 50 Australian sparkling white wines, representing the four key production methods, that is, Méthode Traditionelle (n = 20), transfer (n = 10), Charmat (n = 10), and carbonation (n = 10), were studied. Méthode Traditionelle wines were typically rated highest in quality and were higher in alcohol and protein contents, but lower in residual sugar and total phenolics, than other sparkling wines. They also exhibited higher foam volume and stability, which might be attributable to higher protein concentrations. Bottle-fermented Méthode Traditionelle and transfer wines contained greater proportions of yeast-derived mannoproteins, whereas Charmat and carbonated wines were higher in grape-derived rhamnogalacturonans; however, total polysaccharide concentrations were not significantly different between sparkling wine styles. Free amino acids were most abundant in carbonated wines, which likely reflects production via primary fermentation only and/or the inclusion of nontraditional grape varieties. Fatty acids and their esters were not correlated with foaming properties, but octanoic and decanoic acids and their ethyl esters were present in Charmat and carbonated wines at significantly higher concentrations than in bottle-fermented wines and were negatively correlated with quality ratings. Research findings provide industry with a better understanding of the compositional factors driving the style and quality of sparkling white wine.

Toward a model of sparkling wine purchasing preferences

Purpose This paper aims to provide further insight into factors influencing Australian consumers’ purchasing preferences for sparkling wine, including champagne. Design/methodology/approach Focus groups were conducted and thematic analysis was undertaken to identify factors influencing sparkling wine consumers’ purchasing preferences. Findings Personal taste was found to influence choice of a sparkling wine rather than another type of beverage, and selection of a particular style and brand of sparkling wine. Country or region of origin was found to be important, often linked to the product being champagne. Brand image, reputation and symbolism were found to influence purchase decisions (sometimes linked to consumption occasion), especially for purchases of gifts. Advice, recommendations and expert reviews, and consumption occasion also were found to influence purchase decisions. Price was found to influence style and brand of sparkling wine purchased. A high price was found to be a barrier for some participants, while other participants were found to avoid sparkling wines priced below some particular level. Thematic analysis enabled development of a preliminary model of purchasing preferences. Research limitations/implications Being exploratory in nature, findings cannot be generalised. Further studies are required to confirm the preliminary model and to evaluate the validity and significance of proposed relationships. Practical implications Findings suggest a producer could benefit from marketing a range of sparkling wines to cater to different tastes, occasions and gift purchases. Findings also confirm the importance of marketers pursuing opportunities to obtain and promote favourable expert reviews for their sparkling wines, and of identifying and promoting regional distinctiveness. Originality/value The first comprehensive model of sparkling wine consumers’ purchasing preferences has been developed. Empirical testing would enable refinement and enhance understanding.

Accumulation of guaiacol glycoconjugates in fruit, leaves and shoots of Vitis vinifera cv. Monastrell following foliar applications of guaiacol or oak extract to grapevines

Previous studies have shown that volatile compounds present within a vineyard during the growing season can be absorbed by grapevines, assimilated within grapes, and then released during fermentation to influence the final aroma of wine. For example, the accumulation of volatile phenols in glycoconjugate forms following grapevine exposure to bushfire smoke, and their subsequent release during winemaking. This study investigated the accumulation of guaiacol glycoconjugates in the fruit, shoots and leaves of Monastrell grapevines following foliar applications (at veraison) of either an aqueous solution of guaiacol or an aqueous oak extract. Fruit, shoot and leaf samples were then collected at 3 time points between veraison and maturity, and analysed by gas chromatography-mass spectrometry and liquid chromatography-tandem mass spectrometry, to quantify guaiacol and its glycoconjugates, respectively. Guaiacol glycoconjugates were observed in fruit and leaves in particular, demonstrating glycosylation occurred after grapevine treatment; however, different glycoconjugate profiles were apparent.

Accumulation of Glycoconjugates of 3-Methyl-4-hydroxyoctanoic Acid in Fruits, Leaves, and Shoots of Vitis vinifera cv. Monastrell following Foliar Applications of Oak Extract or Oak Lactone.

Grapevines are capable of absorbing volatile compounds present in the vineyard during the growing season, and in some cases, volatiles have been found to accumulate in fruits or leaves in glycoconjugate forms, that is, with one or more sugar moieties attached. The presence of oak lactone in wine is usually attributable to oak maturation, but oak lactone has been detected in wines made with fruit from grapevines treated with oak extract or oak lactone. This study investigated the accumulation of glycoconjugates of 3-methyl-4-hydroxyoctanoic acid (i.e., the ring-opened form of oak lactone) in the fruits, leaves, and shoots of Monastrell grapevines following foliar application of either oak extract or oak lactone at approximately 7 days postveraison. Fruits, leaves, and shoots were collected at three different time points, including at maturity. The oak lactone content of fruit was determined by gas chromatography-mass spectrometry, with declining concentrations observed in fruit from grapevines treated with oak lactone with ripening. The concentrations of a β-d-glucopyranoside of 3-methyl-4-hydroxyoctanoic acid in fruits, leaves, and shoots was determined by liquid chromatography-tandem mass spectrometry, with the highest oak lactone glucoside levels observed in leaves of grapevines treated with oak lactone. A glucose-glucose disaccharide was also tentatively identified. These results demonstrate both ring-opening and glycosylation of oak lactone occurred after experimental treatments were imposed.

Sensory profiles and consumer acceptance of different styles of Australian Moscato

Background and Aims In recent years, there has been significant growth in the popularity, and therefore sales, of Moscato in Australia. The aim of this study was to determine the sensory and quality variation amongst Australian Moscato wines, as well as consumer acceptance of different styles of Moscato. Methods and Results The sensory profile of 24 Australian Moscato wines was determined by descriptive analysis using a trained panel, while quality ratings were determined by an expert panel of sparkling winemakers and wine show judges. Statistical analysis of sensory attribute ratings facilitated selection of a subset of Moscato wines, comprising three white and three pink wine styles that reflected the sensory variation observed amongst all wines, which were subsequently used in acceptance trials to determine consumer liking. Conclusions Considerable diversity was observed amongst the composition and sensory profiles of the Moscato wines studied, with some exhibiting more prominent varietal characters, while others displayed complex, developed notes. Mean hedonic ratings for the subset of Moscato wines ranged from 4.7 to 5.6 (on a 9 cm scale). Segmentation of consumers according to their individual liking scores enabled identification of two consumer clusters with opposing preferences for distinct styles of Moscato. Significance of the Study The variation in sensory profiles and quality of Australian Moscato wines has been profiled for the first time and consumer acceptance of different styles of Moscato determined. These results enable industry to make more informed decisions with regard to wine production and marketing, that is, to tailor different styles of Moscato for specific segments of the domestic sparkling wine market.

Soluble Protein and Amino Acid Content Affects the Foam Quality of Sparkling Wine

Proteins and amino acids are known to influence the foam characteristics of sparkling wines. However, it is unclear to what extent they promote foam formation and/or stability. This study aimed to investigate the effect of protein content and amino acid composition, measured via the bicinchoninic acid assay and high-performance liquid chromatography, respectively, on the foaming properties of 28 sparkling white wines, made by different production methods. Foam volume and stability were determined using a robotic pourer and computer vision algorithms. Modifications were applied to the protein determination method involving the use of yeast invertase as a standard in order to improve quantification accuracy. The protein content was found to be significantly correlated to parameters representative of foam stability, as were the amino acids arginine, asparagine, histidine, and tyrosine. Additionally, the production method was found to influence the foam collar height, which favored foaming in Méthode Traditionnelle wines over other those made by production methods. Understanding the contributions of key wine constituents to the visual and mouthfeel parameters of sparkling wine will enable more efficient production of high-quality wines.